The Malleo is actually a big spring creek. It flows out of Lake Tromen as a very small free-stone mountain stream. Once it hits the beautiful Malleo Valley the river starts receiving spring water from numerous tributary spring creeks including the Huaca Mamuil, the Mamuil Malal, the Tres Picos, and several others.
Virtually 90% of the Malleo River water is spring water. This unique feature makes for a
river with consistent water temperature and conditions; hence underwater life is rich and varied, from profuse insect life (nymphs, larva, pupa, mayflies, caddis, stoneflies) to countless terrestrials and “pancora” crabs; all this makes for a unique population of sizable and healthy browns and rainbows.
The Malleo may be the truly complete river. It has diverse conformations: from its scenic meadow section, with the Lanín Volcano dominating the background, to the canyon section or the lower boulder bottomed section which offers pocket water and willow-lined banks. It is just the “right size” river to fish and wade and you will always see hatches of different types: caddis and mayflies of various kinds, as well as stoneflies and midges. This river offers dry-fly and sight-fishing opportunities along its 20 kilometers. It is like textbook fishing, the classic way.